Oh I believe there is other intelligent life in space - Its too big for there not to be.
I just don't believe we are being studied, visited or grown by any of them. Given the age and size of the universe, the commoness of our type of star sytem and planets, The vast distances that would be needed to be travelled seem too great of an expendature to justify the limited and recent activity that is being promoted.
Its like all the ships in Star Trek and Star Wars arriving at a destination upright to each other. It could happen but it is highly unlikely.
Time is a factor that should not be dismissed. Per string theory, the possibility of other dimensions is very likely. Crossing a timestream, if one could be isolated, may allow one to cross to the same stream like walking thru a door. Think of a string that crosses against itself.
It may not be time travellers but dimension travellers. Perhaps the sighting are beings from another dimension but of our relative universal coordinates. They have developed the ability to open gateways to other dimensions of space.
Its easier for me to grasp a being geting in his buggy and flipping some controls and phasing into our time stream/dimension than it is for me to believe a being getting in his buggy and setting off on a major journey to our little planet just to study us.
One must also take into account that intelligent beings are not likely to be bipedal, with 2 eyes, 1 mouth one head a torso and arms. Also lets not forget that the size of a being is relative to the characteristics of its home planet, star properties and metabolism.
Lets assume that a being evolves to intelligence on a planet with all the same parameters as ours. If not for a freak accident that changed the dominate life form on our planet 65 million years ago we likely would not exist as we do today. Our limbs may have grown similar and out features may have developed but one of the driving forces of our intelligence was that we had a chance to change. If there was not great dying 65 million years ago we would have remained a food item cowering in the shadows of the monsters that hunt us.
Now lets assume that the beings are the dominate lifeform of their planet and did grow similar to the way we developed. Being a dominate life form would create a whole new set of imperatives in their hunter/gatherer style. Their values would be very different. Being a dominate species they would have a confidence of their own superiority that would penetrate into how they would act toward other life forms. To assume that they would have any values in common to us is extremely pushing it.
Now, a being that developed on our planet, evolved from our body style and possessing our fundamental values and associations may resemble the beings as described in the common encounter story. Those beings would need to isolate their encounters and work in secrecy because they would relate to our values and fears.
As much as I would like to think that ET is visiting us and technology for FTL travel is possible it just seems too far fetched to be a reality.